In many manufacturing processes, color is often a key parameter that must be controlled. To control color quality, high precision spectrophotometers have been used to evaluate incoming raw materials and finished products to attempt to address issues with color. However, an obstacle to accurate and consistent color measurement arises from the fact that environments in which “on-line” or “in process” measurements of manufactured products need to be conducted are typically more challenging than environments in which raw materials or finished products are evaluated. There is an unsatisfied need for more industrially robust instrument solutions that can better enable color measurement capability at various stages throughout a manufacturing process. Instruments are needed that can maximize the volume of materials and products that can be inspected; and that permit measurements to be conducted at different stages of industrial processes to allow more effective opportunities for corrective action and thereby reduce material waste, product rework and downtime.
In particular, the capacity to make non-contact color (“NCC”) measurements is lacking in many devices. For example, a sample to be measured may have a finished surface that should not be touched at certain stages of production, such as in the case of many painted automotive parts. In certain manufacturing processes, the desired point of measurement for a component or material is at a stage in production when the component is still wet or soft and contact with a measurement device would damage or mar the component. In other situations, NCC measurement may be desirable because a part is too hot to be touched or should not be contaminated by contact, such as in the case of the food processing industry.
Also, the distance between a sample and the sensor of the measurement device sensor often varies during production, and this can adversely impact measurement consistency. In many manufacturing environments, adequate staging of a sample to be tested that would allow repeatable measurement distance control is not practical or feasible. Traditional color measurement devices are usually negatively affected by the “inverse square law” with respect to illumination, sensing, or both. Devices and processes are needed that can reduce or compensate for the measurement distance variations inherent in many manufacturing processes.
Another factor is the capability to make NCC measurements in ambient light. In many cases, it is not easy to find a sufficiently darkened location on a sample from which to derive a suitable measurement. One possible solution is to overpower the ambient light conditions by using a high power xenon flash illumination, for example, with the instrument. This solution is problematic, however, because it does not work well with samples that have photochromatic properties, and there are product power and life cycle issues presented by the use of such illumination.
In addition, devices need the ability to make color measurements in industrial environments affected by temperature, vibration, and the presence of particulate or liquid contaminates. Such devices need to be capable of providing stable measurements independent of the operating temperature of the environment, for example. Shock and vibration, humidity, particulate or liquid contamination, and cleaning operations must be endured by the sensing or illumination ports of the devices without affecting their measurement capacity.
Furthermore, high intensity and good uniformity of illumination is usually advantageous to the illumination system of a color measurement device. However, high quality illumination often requires a complicated light collecting lens system specially designed to eliminate spherical aberrations and other undesirable effects. In another approach, in a more simplified system, if an increase in light intensity is attempted by collecting light from a larger cone angle, for example, then the uniformity of the illumination can be impacted due to the effects of spherical aberrations.
In view of the foregoing issues, what are needed are more effective and efficient devices, structures and processes for measuring color, especially in industrially challenging environments.